Highly malleable, ductile zinc strip

ABSTRACT

The present invention refers to a zinc strip comprising zinc as main component, wherein titanium and aluminium are alloyed together with the zinc. The obtained zinc strip is highly malleable and at the same time ductile. The zinc strip is free of lead.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to European patent application 18176438.2 filed Jun. 7, 2018 which is incorporated herein by reference.

TECHNICAL FIELD

The present invention refers to a zinc strip comprising zinc as main component, wherein titanium and aluminium are alloyed together with the zinc. The obtained zinc strip is highly malleable and at the same time ductile. The zinc strip is free of lead. The zinc strip according to the present invention is ductile and the therefrom resulting high formability enables the skilled artisan to use the zinc strip especially in roofing applications.

INTRODUCTION AND SUMMARY OF THE INVENTION

Until today, usually lead is used in roofing applications, i.e. ceilings of dormers on a roof, transitions on a roof area etc. Lead is getting less and less accepted by the public due to its toxicity for humans. None of the alternative materials shows sufficient malleability and ductility for the above-mentioned applications. Thus, it is the object of the present application to provide a zinc strip which is free of lead. At the same time, it shall be highly malleable and ductile. It should of course not be toxic. Surprisingly, it was found that alloying zinc with low amounts of titanium and aluminium enables the production of a highly malleable zinc strip.

DETAILED DESCRIPTION OF THE INVENTION

Thus, in a first embodiment the present invention is solved by a zinc strip comprising zinc as main component and further comprising titanium as well as aluminium. The amount of titanium is 500 ppm or less and the amount of aluminium is 100 ppm or less. In another embodiment, the present invention refers to the use of a respective zinc strip in the field of roofing. In another embodiment, the present invention refers to a method to produce a zinc strip with defined low amounts of titanium and aluminium.

Surprisingly it was found that a zinc strip with a defined low amount of titanium and aluminium, which are alloyed with the zinc, enables to produce a highly malleable, ductile zinc strip. Further surprisingly it was found that when producing a zinc strip, quite low temperatures of about 100° C. are sufficient together with a high number of rolling passes to increase the malleability and ductility of the zinc strip.

The zinc strip of the present invention is obtained by alloying zinc with titanium and aluminium. The amount of titanium and aluminium should be quite low, namely 500 ppm or less and 100 ppm or less respectively. At the same time, the presence is needed to obtain the improved mechanical properties. Preferably, the amount of titanium is at least 10 ppm and the amount of aluminium is at least 10 ppm as well.

In a preferred embodiment, the zinc strip further comprises copper. This copper will not be alloyed but is part of the used zinc. The amount of copper in the zinc strip is preferably 500 ppm or less. Higher amounts of copper would result in worse mechanical properties, such as malleability and ductility.

Zinc usually comprises impurities. Known impurities are Pd, Cd, Fe and Sn. The amount of impurities especially of the ones cited before is preferably 0.05% by weight or less, especially 0.01% by weight or less, especially preferred 0.005% by weight or less, based on the total weight of the zinc strip. Surprisingly it was found that highly pure zinc with a defined low amount of copper can be alloyed with titanium and aluminium and the thus obtained alloy can be used to obtain zinc strips with good mechanical properties, especially malleability and ductility.

To have a low amount of total impurities, the zinc used to prepare the zinc strip is preferably high purity zinc according to classification Z1 of DIN EN 1179:2003. Using this highly pure zinc to produce the zinc strip enables to reduce and control the amount of total impurities and also to control the amount of copper in particular. Thus, in a preferred embodiment zinc of classification Z1 of DIN EN 1179:2003 is provided and titanium as well as aluminium are alloyed to obtain the zinc strip of the present invention which comprises zinc as main component. The amount of titanium is 500 ppm or less and the amount of aluminium is 100 ppm or less. Due to the use of their high purity zinc, also the amount of copper is 500 ppm or less.

In a preferred embodiment, the amount of titanium is 300 ppm or less, especially 100 ppm or less, preferably 50 ppm or less. The amount of aluminium is preferably 50 ppm or less. The amount of copper, where applicable, is preferably 300 ppm or less, preferably 100 ppm or less, especially 50 ppm or less, preferred 20 ppm or less.

The ratio of masses of aluminium and titanium being present in the zinc strip is preferably in the range of from 1:5 to 5:1, especially from 2:3 to 3:2, preferred from 1:2 to 2:1, it may also be 1:1, so that the amount of aluminium and titanium is approximately the same.

Amounts in ppm or percent by weight usually refer to the total weight of the zinc strip if not explicitly indicated different.

Using the high purity zinc and controlling the amount of titanium and aluminium and, where applicable, copper, enables as mentioned above to obtain a zinc strip with improved mechanical properties. Respective mechanical properties are for example tensile strength and yield strength. In the following Table 1, respective values are shown. Here, an inventive zinc strip is compared with known prior art substances.

TABLE 1 Mechanical properties of different material tensile strength yield strength Material (Rm) [Rp 0.2] Titanium-Zinc min. 150 MPa min. 100 MPa Copper 220-260 MPa max. 140 MPa Stainless steel 500-700 MPa ≥190 MPa Galvanized steel 260-420 MPa 120-220 MPa Leadfree zinc strip <120 MPa <60 MPa according to the present invention

Compared to known titanium zinc alloys, the zinc strip of the present invention differs especially in its chemical composition, where the amount of titanium, aluminium and copper, where applicable, are much lower than in known products. The chemical composition of titanium zinc compared with the zinc strip of the present application is shown in the following Table 2.

TABLE 2 chemical composition (all values in % by weight) Leadfree zinc strip according to the present Titanium-Zinc invention Copper 0.08-1.0% <0.002% Titanium 0.06-0.2% <0.005% Aluminium max. 0.015%   <0.005%

In a preferred embodiment, the present invention refers to a zinc strip based on lead free zinc according to classification Z1 of DIN EN 1179:2003 which comprises 300 ppm or less titanium, 50 ppm or less aluminium as well as 300 ppm or less copper besides zinc as main component. In another preferred embodiment, the present invention refers to a zinc strip comprising zinc as main component, wherein the zinc is a high purity zinc according to Z1 of DIN EN 1179:2003, said zinc strip comprising 100 ppm or less titanium, 50 ppm or less aluminium as well as 100 ppm or less copper.

Also preferred is a zinc strip based on high purity zinc according to classification Z1 of DIN EN 1179:2003 comprising 100 ppm or less titanium, 50 ppm or less aluminium as well as 50 ppm or less copper. In another preferred embodiment, the zinc strip is based on high purity zinc according to classification Z1 of DIN EN 1179:2003 and further comprises 50 ppm or less titanium, 50 ppm or less aluminium as well as 20 ppm or less copper.

In another preferred embodiment, the zinc strip is based on a high purity zinc according to classification Z1 of DIN EN 1179:2003 further comprising titanium and aluminium, wherein the amount of titanium is 50 ppm or less, the amount of aluminium being 20 ppm or less and the amount of copper stemming from the zinc is 20 ppm or less. Further preferred is an embodiment in which a zinc strip being based on high purity zinc according to classification Zi of DIN EN 1179:2003 comprises 20 ppm or less titanium, 50 ppm or less aluminium as well as 20 ppm or less copper.

The zinc strip according to the present invention preferably has a thickness of 0.1 mm to 2.5 mm, especially 0.15 mm to 2.0 mm, preferably from 0.2 mm to 1.5 mm, preferred from 0.2 mm to 1.0 mm, especially preferred from 0.2 mm to 0.6 mm. These thicknesses enable good handability so that the zinc strip can be used in roofing applications, such as ceilings or transitions in roof areas, sealing a dormer of a roof, transitions in a roof area, roof ridges, eaves, chimney or wall connection, skylights, or to connect roof gutters.

It is within the invention, that the zinc strip may be coated with a colour so that it is not or at least hardly not visible after application. For a better application, it may also be possible that the zinc strip comprises an adhesive on one outer surface so that the strip can be applied to the area where it is used.

It is to be noted, that the thickness mentioned above refers to the thickness of the zinc strip only without a colour coating and/or an adhesive coating. The thickness of the colour coating, where present, is only several μm (usual values are in the range of 10 μm to 50 μm, especially 15 μm to 35 μm), so that it is not relevant for the thickness of the strip in total. The thickness of the adhesive, where present, is preferably within a range of from 0.1 mm to 1 mm, especially from 0.2 mm to 0.8 mm, preferred from 0.3 mm to 0.7 mm, especially preferred from 0.3 mm to 0.6 mm or to 0.5 mm. Preferably, the thickness of the adhesive is nearly the same or less than the one of the zinc strip. The ratio between the thickness of the adhesive and the thickness of the zinc strip is therefore in a preferred embodiment in a range of from 1:5 to 2:1, especially from 1:2 to 1:1.

The total thickness of a strip with adhesive is preferably in a range from 0.2 mm to 3.5 mm, especially from 0.3 mm to 2.5 mm, preferred from 0.5 mm to 1.5 mm, especially preferred from 0.6 mm to 1.2 mm, preferably from 0.7 mm to 1 mm. If the strip comprises not only an adhesive but also a colour coating the total thickness remains more or less the same.

The colour can be any suitable colour known by the skilled artisan. Suitable colours can be varnishes, such as alkyd varnish, epoxy resin varnish, polystyrene- or polyvinyl resin varnishes, phenolic varnish, urea varnish, melamine resin varnish or polyurethane varnishes. Varnishes based on polyurethane are especially preferred due to their high resistance against solvents, chemicals as well as whether influences. This enables a long colour during outdoor use.

In another preferred embodiment, the zinc strip comprises an adhesive on only one of the outer surfaces. The adhesive is added in such a way, that the zinc strip can be fixed on the area to be used. Thus, the adhesive may be coated on the complete out surface of the zinc strip. It is also within the invention that the adhesive is on the other part of the one outer surface, such as in strips, points or that only specific areas to be connected with a specific basis are coated with an adhesive. It is to be noted, that the adhesive is only on one outer surface of the zinc strip, which is the surface to be added to the roof for example. The opposite surface will then be visible in use. This visible surface will of course not comprise any adhesive.

Suitable adhesives are for example adhesives based on acrylates, epoxides, phenolics, silicones, polyamides or adhesive tapes based on butyl. Acrylate adhesives and especially solvent free acrylate adhesives are especially preferred.

Preferred adhesives, especially the acrylate-based adhesives have the following advantages: High initial strength, good impact strength, high shear strength, UV resistance, good resistance against the influence of water, structural strength, goof wetting behaviour, can be applied to many surfaces, good resistance against changes in temperature, good resistance against influences of chemicals, as well as good aging resistance. Due to these advantages, adhesives based on acrylates are especially preferred, in particular those which are free of any solvents, as they enable a good adhesion in use and stability against all kind of weather effects.

In another embodiment, the present invention refers to a method of producing a zinc strip. The method includes providing zinc plates based on zinc. These plates further comprising titanium and aluminium where the amount of titanium is 500 ppm or less and the amount of aluminium is 100 ppm or less. To obtain such zinc plates, a zinc is alloyed together with titanium and aluminium in amounts such that the mentioned amounts are obtained. Preferably, the zinc is high purity zinc according to classification Z1 of DIN EN 1179:2003, preferably the amount of copper in the zinc is such that the amount of the zinc strip is 500 ppm or less.

The zinc plates are preferably made by continuous casting. In the beginning, the zinc plates are headed to a temperature of about 100° C. or more. In the following, the plates are rolled as long as needed to obtain the thickness needed for using the strips in roofing applications.

The number of rolling passes needed to obtain the respective thickness is preferably 10 or more. It is advanteougous to have a discontinuous per pass reduction rate during the rolling process which is dependent on temperature and pressure during the rolling.

The final temperature of the rolling process is preferably about 50° C. or more. The parameters of initial temperature, number of rolling passes, discontinuous prepass reduction rate as well as final temperature of the rolling process are relevant as all these features together and especially the initial temperature as well as the number of rolling passes enables the production of a zinc strip with high ductility and advantages mechanical properties. The method of the present invention enables the production of a zinc strip where the formation of coarse grains is avoided. This result in the excellent mechanical properties described above.

It is of course within the scope of the present invention that during the rolling process a rolling oil or an oil-based emulsion might be used.

Any embodiments disclosed in the specification can be combined with any other embodiment, even if not explicitly mentioned. Features disclosed for the method are also applicable for the zinc strip and vice versa. 

1. Zinc strip comprising zinc as main component titanium, and aluminum, wherein an amount of titanium is 500 ppm or less, and the amount of aluminium is 100 ppm or less.
 2. Zinc strip according to claim 1, wherein the amount of titanium is at least 10 ppm, and the amount of aluminum is at least 10 ppm.
 3. Zinc strip according to claim 2, further comprising copper in an amount of 500 ppm or less.
 4. Zinc strip according to claim 1, wherein the zinc comprises impurities that include Pb, Cd, Fe, and/or Sn, wherein the total amount of impurities amount to 0.05% by weight or less based on the total weight of the zinc strip.
 5. Zinc strip according to claim 1, wherein the zinc is a high purity zinc according to classification Z1 of DIN EN 1179:2003.
 6. Zinc strip according to claim 1, wherein the amount of titanium is 300 ppm or less.
 7. Zinc strip according to claim 1, wherein the amount of aluminum is 50 ppm or less.
 8. Zinc strip according to claim 3, wherein the amount of copper is 300 ppm or less.
 9. Zinc strip according to claim 1, having a thickness of 0.1 mm to 2.5 mm.
 10. Zinc strip according to claim 1, said strip being coated with a colour.
 11. Zinc strip according to claim 1, said strip comprising an adhesive on one outer surface.
 12. A method of roofing comprising use of a zinc strip according to claim 1 for sealing a dormer of a roof, transitions in a roof area, roof ridges, eaves, chimney or wall connection, skylights, or to connect roof gutters.
 13. Method to produce a zinc strip according to claim 1 comprising: a) providing zinc plates based on zinc and further comprising titanium, and aluminum, wherein the amount of titanium is 500 ppm or less, the amount of aluminum is 100 ppm or less, b) warming the plates to a temperature of about 100° C. or more and c) rolling the plates.
 14. Method according to claim 13, wherein a number of rolling passes in step c) amounts to 10 or more.
 15. Method according to claim 14, wherein a discontinuous per pass reduction rate is obtained during the rolling process.
 16. Method according to claim 13, wherein the final temperature of the rolling process is about 50° C. or more. 